The present invention relates to electrical machinery and, more particularly, to high frequency synchronous rotary electrical generators and motors.
FIG. 1 shows, in axial cross section, a high frequency synchronous rotary electrical generator 10 of the prior art. Projecting radially inwardly from the inner wall of a cylindrical yoke 12 are a plurality of stator teeth 14, around which are wound armature windings 16. There are two groups of stator teeth 14, on either axial side of an annular excitation winding 18 that is rigidly attached to and concentric with yoke 12. Also concentric with yoke 12, and rotatably mounted within yoke 12 on bearings (not shown), are a shaft 20 and a rotor 22. A plurality of rotor teeth 24 project radially outward from rotor 22 opposite stator teeth 14. Note that armature windings 16 are wound, through the slots that define stator teeth 14, in planes that are parallel to shaft 20.
Windings 14 and 16 are made of a good electrical conductor such as copper wire or aluminum wire. Yoke 12, stator teeth 14, rotor 22 and rotor teeth 24 are made of a ferromagnetic material such as iron, so that when a DC current is applied to excitation winding 18, a poloidal magnetic field, represented by dashed loops 26, is set up through yoke 12, rotor 22, and teeth 14 and 24. Turning shaft 20 sweeps teeth 24 past teeth 14, causing a temporal variation in the magnetic flux linking teeth 24 and 24, thereby inducing an AC EMF in armature windings 16.
There are at least two deficiencies in the design of generator 10. One is that generator 10 is structurally inefficient, inasmuch as the portions of armature windings 16 that project axially beyond rotor teeth 14 do not participate in torque creation. The other is that it is difficult to automate the winding of windings 14. In large versions of generator 10, windings 14 are wound by hand.
There is thus a widely recognized need for, and it would be highly advantageous to have, a design for a synchronous rotary electrical machine that is more efficient, and whose construction is easier to automate, than the prior art machines.